Under the Janesick Method [1]}, at least two bias and two flat frames are needed to estimate the gain and RN values. Hence, the bias and flat frames were observed in each readout speed and gain combination. First, we selected a clean region of 100\(\times \) 100 pixels for both the flat and bias frames. Then, we estimated mean counts for both the flat (\(\overline{F_1}\)  and \(\overline{F_2}\) ) and the bias frames (\(\overline{B_1}\)  and \(\overline{B_2}\) ). The difference of the two flat frames was created by subtracting two flat frames to remove flat field variations and estimated the variance of this (\(\sigma ^2_{F_1 - F_2}\) ) and likewise for bias images (\(\sigma ^2_{B_1 - B_2}\) ). The gain and RN of the STA CCD chip were then calculated as:
\(Gain = \frac{(\overline{F_1} + \overline{F_2}) - (\overline{B_1} + \overline{B_2})}{\sigma ^2_{F_1 - F_2} - \sigma ^2_{B_1 - B_2}}\) 
\(RN = \frac{G.\sigma _{B_1 - B_2}}{\sqrt{2}}\) 
